V
vict
Hi,
Id like to get some advice to repair this set. The problem is: bright
horizontal line in the center of the screen and then picture above it,
which occupies about 25% of the screen. Picture compressed at the
center and almost normal at the top of the visible rectangle. So
picture expands gradually in the 25% height of the screen.
I'm familiar with electronic repairs, but not TVs though. I have
digital multimeter and reading different groups already changed all
electrolythics with numbers 3xx and IC301 LA7837, - no difference
whatsoever.
Numbers of capacitors are not typical on this set.
I would throw it away unless this repair was for person who cannot
afford professional repair and to buy a new TV. Also to my desire to
continue investing time in this TV set adds that this person has
another old Toshiba CF27??? TV (same size, one year difference) with
exactly the same problem, so after figuring out this one I might as
well easily fix another for her.
I also checked/replaced one diode in pump up circuit (between pins 8
and 13) - again - no difference. Nothing looks wrong on PCB, also
checked without taking them out several resistors, mostly big ones
around IC301 - all seem good.
Schematic diagram would help, but I missed one recently sold at eBay
for CX2780A & CX29801 in the same book.
I'm observing 9V on pin 1 of IC301 and 0.9V on pin 12. Some other TVs
have 9V, but typical is 12V on pin 1 and on pin 12 I think should be
around half of supply voltage, which is 30V.
(Several other toshibas i found have 27V on schematic diagram).
Signal to IC301 comes from IC501 TA8801N and I'm wondering is there any
sense in replaciing this one or maybe some non-electrolythics.
Reading groups about same fault I see that some people fixed it with
capacitor changes while others with similar issues didn't get any
answers beyond to change el. capacitors.
Any help will be very appreciated
thanks,
Vict
Id like to get some advice to repair this set. The problem is: bright
horizontal line in the center of the screen and then picture above it,
which occupies about 25% of the screen. Picture compressed at the
center and almost normal at the top of the visible rectangle. So
picture expands gradually in the 25% height of the screen.
I'm familiar with electronic repairs, but not TVs though. I have
digital multimeter and reading different groups already changed all
electrolythics with numbers 3xx and IC301 LA7837, - no difference
whatsoever.
Numbers of capacitors are not typical on this set.
I would throw it away unless this repair was for person who cannot
afford professional repair and to buy a new TV. Also to my desire to
continue investing time in this TV set adds that this person has
another old Toshiba CF27??? TV (same size, one year difference) with
exactly the same problem, so after figuring out this one I might as
well easily fix another for her.
I also checked/replaced one diode in pump up circuit (between pins 8
and 13) - again - no difference. Nothing looks wrong on PCB, also
checked without taking them out several resistors, mostly big ones
around IC301 - all seem good.
Schematic diagram would help, but I missed one recently sold at eBay
for CX2780A & CX29801 in the same book.
I'm observing 9V on pin 1 of IC301 and 0.9V on pin 12. Some other TVs
have 9V, but typical is 12V on pin 1 and on pin 12 I think should be
around half of supply voltage, which is 30V.
(Several other toshibas i found have 27V on schematic diagram).
Signal to IC301 comes from IC501 TA8801N and I'm wondering is there any
sense in replaciing this one or maybe some non-electrolythics.
Reading groups about same fault I see that some people fixed it with
capacitor changes while others with similar issues didn't get any
answers beyond to change el. capacitors.
Any help will be very appreciated
thanks,
Vict